Abstract
Spiders of the genus Cybaeus L. Koch, 1868 exhibit two major centers of diversity: Western North America and Japan. Several Japanese Cybaeus possess an elongated embolus in the male palp and elongated tubular spermathecae in the female genitalia. Here we describe Cybaeus koikeisp. nov. from central Honshu, Japan, which has an unelongated embolus and bulbous spermathecae. Phylogenetic analyses using nuclear and mitochondrial gene markers clearly support the monophyly of C. koikeisp. nov. and Cybaeus melanoparvus Kobayashi, 2006, a species with elongated genitalia. Both species share a similar habitus and a cluster of robust setae on the lateral surface of the male palpal patella. The latter is considered a synapomorphy for C. koikeisp. nov. and C. melanoparvus. A supplementary description of the spermathecae of C. melanoparvus is also provided.
Highlights
Epigean spiders of the genus Cybaeus L
The monophyly of C. koikei sp. nov. and C. melanoparvus was strongly supported (BS = 100%, posterior probabilities (PP) = 1.0) but the sister-group of this clade remains unclear since the monophyly of a lineage including C. koikei sp. nov., C. melanoparvus, and C. daimonji Matsuda, Ihara & Nakano, 2020 was not fully supported (BS = 63%, PP = 0.70)
The SplitsTree network (Fig. 3) using internal transcribed spacer 1 (ITS-1) sequences showed all males and females forming a cluster, which was clearly separated from that of C. melanoparvus, confirming that all specimens belong to C. koikei sp. nov
Summary
Epigean spiders of the genus Cybaeus L. 1868 are remarkably diverse in Western North America and the Japanese Archipelago (Copley et al 2009; Ihara 2009a; Bennett et al 2016, 2019, 2021). 91 of the 174 known Cybaeus species have been described from Japan (World Spider Catalog 2021) and they have been classified according to the body length of mature individuals (Ihara 2004): ‘small-sized’ The extraordinary species-richness of Japanese Cybaeus may be caused by ecological attributes, such as poor dispersal abilities. Cybaeus spiders are not known to disperse via ballooning (Copley et al 2009) and this may lead to range restriction in many species. These species may be classified as species groups (= ‘superspecies’ in Ihara 2008) but the monophyly of each group is yet to be confirmed by molecular phylogenetic analyses
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